DWP & problems with executor

My late mum died in March 2019 this year. I registered her death & used the Tell Us Once service. In June I received 2 letters stating there had been a slight overpayment in her benefits just over £200. No matter. This will be paid when her property sells very shortly.

A couple of months later, the DWP have written to the executor after probate has been granted. No doubt alerted to the value of the estate as it includes the value of her property. Is it my understanding that he should tell them that what is down as the value is mainly her property?
He recorded the conversation & sent it to me & I was not impressed since the person he spoke to was scare mongering him into thinking that my mum might owe thousands.

As far as I am aware, my mum was on the correct benefits including her pension credit.
She was 90 when she died so would she have been in receipt of something that I read AIP?

I am the main beneficiary of her will & apart from her will bequests, the rest of her estate passes to me. Her house sale should complete next week & with the proceeds I am buying a house, much less value. As I am self employed & had to empty her bungalow which had 50 yrs of hoarding in it, I virtually had to give up work for 5 months. The executor did not help me in this task at all despite me asking him several times.

The executor has been giving me some money to live off from my mum’s bank accounts which will pass to me as per the will.
These were granted as they were below the probate threshold & declared as part of her estate.
My mum’s estate was below the Inheritance Tax threshold. There is no income or any other tax to be paid. However now he has been frightened by the DWP, he is refusing to give me any money.
I have read stories on here that it is taking them ages to go through files but surely he would be mad to wait?! Surely if my house purchase does not go through due to his actions then I could end up sueing him? I read of a case that took 2 yrs to come through.

I have told him that as I have signed my purchase contract that I am bound by it now - if he made me pull out then I would lose the reservation deposit which was £4800.
If my mum’s estate does owe money then I have said that everyone including myself would have to have a cut of their inheritance taken so it can be paid. This was even suggested by the DWP.

But even so, after the house sells plus what is left in the bank accounts, there is more than enough money but he has made some miscalculations & last week refused to give me any money that I needed to pay for rent & bills. I had to ring him & have serious words with him before he admitted he had miscalculated & then gave me the money.

I have helped him administer probate every step of the way. Actually I will go further than that, i’ve done most of it in order to save the estate & myself money. I know that it is his discretion to give me money but surely he has a duty to ensure that I am
financially ok & not put in any hardship through this?

My cousin is horrified at his actions in all of this & thinks he is into some kind of power game with me & it has all gone to his head.
I am seeing a solicitor for a free half hr session in a few days but any advice in this would be gratefully received.
We are also in dispute about a 2nd funeral for my mum’s ashes & he wants to go against the wishes of 3 family members. He is not a family member.